3、進程間通信-信號

1、使用sigaction函數 安裝信號（signal函數也可以）

code：

#include<stdio.h> #include<stdlib.h> #include<signal.h> void myHandler(int sig); int main() { struct sigaction act,oact; act.sa_handler=myHandler; sigemptyset(&act.sa_mask); act.sa_flags=0; sigaction(SIGUSR1,&act,&oact); while(1) { printf("Hello world/n"); pause(); } } void myHandler(int sig) { printf("Signal got:%d/n",sig); }

 

2、信號應用sample
     父進程：執行文件拷貝操作，接受SIGUSR1信號，打印拷貝進度
     子進程：每隔一個固定時間（自發SIGALRM信號），向父進程發送SIGUSR1信號。

codes：

#include<stdio.h> #include<fcntl.h> #include<unistd.h> #include<stdlib.h> #include<string.h> #include<signal.h> int count; //the current copy number int file_size; void sig_alarm(int arg); void sig_usr(int sig); int main(int argc,char *argv[]) { pid_t pid; int i; int fd_src,fd_des; char buf[128]; if(argc!=3){ printf("usage error/n"); return -1; } fd_src=open(argv[1],O_RDONLY); if(fd_src==-1){ perror("open"); exit(EXIT_FAILURE); } file_size=lseek(fd_src,0,SEEK_END); lseek(fd_src,0,SEEK_SET); fd_des=open(argv[2],O_RDWR|O_CREAT,0644); if(fd_des==-1){ perror("open"); exit(EXIT_FAILURE); } pid=fork(); if(pid==-1){ perror("fork"); exit(EXIT_FAILURE); } else if(pid>1) { //parent signal(SIGUSR1,sig_usr); do{ memset(buf,0,128); i=read(fd_src,buf,1); if(i==-1){ perror("read"); exit(EXIT_FAILURE); } else if(i==0){ kill(pid,SIGINT); break; } else{ if(write(fd_des,buf,i)==-1){ perror("write"); exit(EXIT_FAILURE); } count+=i; } }while(i!=0); wait(pid,NULL,0); exit(EXIT_SUCCESS); } else if(pid==0){ //child usleep(1); signal(SIGALRM,sig_alarm); ualarm(1000,1000); while(1) { ; } exit(EXIT_FAILURE); } } void sig_alarm(int arg) { kill(getppid(),SIGUSR1); } void sig_usr(int arg) { float i; printf("count:%d size:%d/n",count,file_size); i=(float)count/(float)file_size; printf("current over :%f%/n",i*100); }

結果：

。。。
count:9694673 size:9696669
current over :99.979416%
count:9694899 size:9696669
current over :99.981750%
count:9695107 size:9696669
current over :99.983887%
count:9695300 size:9696669
current over :99.985878%
count:9695498 size:9696669
current over :99.987923%
count:9695712 size:9696669
current over :99.990128%
count:9695898 size:9696669
current over :99.992050%
count:9696072 size:9696669
current over :99.993843%
count:9696298 size:9696669
current over :99.996170%
count:9696539 size:9696669
current over :99.998657%